I saw this picture of the internal heating elements of the mighty. I hadn't seen it before so I wanted to share!
Pretty neat: you can see the thermocouple in the bottom left of the heating chamber to track temp, the air path spirals up the element picking up convective heat, and you can see the hottest spot is in contact with the herb bowl which gives it the conductive heating. Superbly designed device!
How difficult was it to replace the batteries?
It wasn't too bad. Took maybe an hour to complete. You'll need to do some soldering and you'll need to rebuild the internal battery assemblies with some kapton tape. Pay particular attention to how the wires are run on the assemblies or you'll have difficulty making the case fit back on. Honestly the most difficult part was sourcing the batteries with the tabs already welded on. While I'd love having a battery tab spot welder, I just don't think I would use it enough to justify the space to keep one around.
IIRC it can be done with a bunch of 9v batteries connected together